Intel P8700 Data Sheet - Page 108

Thermal Specifications and Design Considerations

108

Datasheet

5.1

Monitoring Die Temperature

The processor incorporates three methods of monitoring die temperature:

•

Thermal Diode

• Intel

®

Thermal Monitor

•

Digital Thermal Sensor

5.1.1

Thermal Diode

Intel’s processors utilize an SMBus thermal sensor to read back the voltage/current

characteristics of a substrate PNP transistor. Since these characteristics are a function

of temperature, these parameters can be used to calculate silicon temperature values.

For older silicon process technologies, it is possible to simplify the voltage/current and

temperature relationships by treating the substrate transistor as though it were a

simple diffusion diode. In this case, the assumption is that the beta of the transistor

does not impact the calculated temperature values. The resultant “diode” model

essentially predicts a quasi linear relationship between the base/emitter voltage

differential of the PNP transistor and the applied temperature (one of the

proportionality constants in this relationship is processor specific, and is known as the

diode ideality factor). Realization of this relationship is accomplished with the SMBus

thermal sensor that is connected to the transistor.

The processor, however, is built on Intel’s advanced 45-nm processor technology. Due

to this new processor technology, it is no longer possible to model the substrate

transistor as a simple diode. To accurately calculate silicon temperature use a full bi-

polar junction transistor-type model. In this model, the voltage/current and

temperature characteristics include an additional process dependant parameter which

is known as the transistor “beta”. System designers should be aware that the current

thermal sensors may not be configured to account for “beta” and should work with their

SMB thermal sensor vendors to ensure they have a part capable of reading the thermal

diode in BJT model.

Offset between the thermal diode-based temperature reading and the Intel Thermal

Monitor reading may be characterized using the Intel Thermal Monitor’s Automatic

mode activation of the thermal control circuit. This temperature offset must be

considered when using the processor thermal diode to implement power management

events. This offset is different than the diode Toffset value programmed into the

processor Model-Specific Register (MSR).

Table 27

and

Table 28

provide the diode interface and transistor model specifications.

Table 27.

Thermal Diode Interface

Signal Name

Pin/Ball Number

Signal Description

THERMDA

A24

Thermal diode anode

THERMDC

A25

Thermal diode cathode

Section	Page
Intel® Core™2 Duo Mobile Processor, Intel® Core™2 Solo Mobile Processor and Intel® Core™2 Extreme Mobile Processor on 45-nm Process	1
Revision History	6
1 Introduction	7
1.1 Terminology	8
1.2 References	9
2 Low Power Features	11
2.1 Clock Control and Low-Power States	11
2.1.1 Core Low-Power State Descriptions	13
2.1.2 Package Low-power State Descriptions	15
2.2 Enhanced Intel SpeedStep® Technology	19
2.3 Extended Low-Power States	20
2.4 FSB Low Power Enhancements	21
2.4.1 Dynamic FSB Frequency Switching	21
2.4.2 Enhanced Intel® Dynamic Acceleration Technology	22
2.5 VID-x	23
2.6 Processor Power Status Indicator (PSI-2) Signal	23
3 Electrical Specifications	25
3.1 Power and Ground Pins	25
3.2 Decoupling Guidelines	25
3.2.1 VCC Decoupling	25
3.2.2 FSB AGTL+ Decoupling	25
3.2.3 FSB Clock (BCLK[1:0]) and Processor Clocking	25
3.3 Voltage Identification and Power Sequencing	26
3.4 Catastrophic Thermal Protection	29
3.5 Reserved and Unused Pins	29
3.6 FSB Frequency Select Signals (BSEL[2:0])	29
3.7 FSB Signal Groups	30
3.8 CMOS Signals	31
3.9 Maximum Ratings	31
3.10 Processor DC Specifications	32
4 Package Mechanical Specifications and Pin Information	51
4.1 Package Mechanical Specifications	51
4.2 Processor Pinout and Pin List	59
4.3 Alphabetical Signals Reference	93
5 Thermal Specifications and Design Considerations	101
5.1 Monitoring Die Temperature	108
5.1.1 Thermal Diode	108
5.1.2 Intel® Thermal Monitor	109
5.1.3 Digital Thermal Sensor	111
5.2 Out of Specification Detection	112

Intel P8700 Data Sheet - Page 108

Monitoring Die Temperature, 5.1.1 Thermal Diode, Thermal Diode

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